1. Field of the Invention
The present invention relates to an apparatus for holding and/or conveying articles by fluid, and, more particularly, to an article holding and/or conveying apparatus for conveying articles such as semiconductor wafers and magnetic discs, which should be kept free from dust or foreign matter, floating on holding or conveying surfaces by fluid pressure under clean conditions.
2. Description of the Prior Art
A conveying apparatus for conveying articles under a clean condition is proposed in, for example, U.S. Pat. No. 4,211,505, wherein a first gas injection portion for supplying an air jet for floating the articles away from the conveyor surface and driving the articles in the delivery direction and a second gas injection portion for supplying air jet to impinge against peripheral edges of the opposite surfaces of the article are provided in a conveyor surface of a delivery path in order to prevent the articles moving on the delivery path from shifting in a direction perpendicular to the delivery direction and from falling apart from the delivery path.
Recently, there has been an increase in the demands for keeping clean the environment around the manufacture process as electronic parts become more fine with higher density. More specifically, it is one of the important tasks to be solved that the articles be conveyed under the condition that the surfaces of the articles be free from the dust. With respect to the demands, since the articles are delivered out of the contact with the conveyor according to the prior art, it would be possible to avoid the dust adhesion due to the contact of the delivery path. However, the air jets for floating, driving and guiding the articles cause the ambient dust to be entrained to form floating dust and, as a result, the dust adheres to the surfaces of the articles. Also, downward flows for preventing to prevent the floating dust contained in the ambient air from adhering to the article surfaces is turbulent so that the dust adhere to the article surfaces.